A biologist who enlisted schoolchildren in his fight to clean up an Indonesian river that led to an international prize said he hoped young people will do more for the environment.

Student research into a 41 km (25 mile) stretch of the Surabaya river that flows through Surabaya, Indonesia’s second-largest city, prompted 35-year-old Prigi Arisandi into discoveries that helped him become one of six winners of this year’s Goldman Environmental Prize, the world’s largest award for grassroots environmentalists…